As is known in the art, there is a trend to reduce the size of semiconductor devices, integrated circuits and microcircuit modules while at the same time having the devices, circuits and modules perform more functions. To achieve this size reduction and increased functionality, it is necessary to include a greater number of active circuits, such as transistors for example, in a given unit area. As a consequence of this increased functionality and dense packaging of active devices, such devices, circuits and modules (hereinafter collectively referred to as xe2x80x9ccircuitsxe2x80x9d) use increasingly more power. Such power is typically dissipated as heat generated by the circuits.
This increased heat generation coupled with the need for circuits to have increasingly smaller sizes has led to an increase in the amount of heat generated in a given unit area. To further exacerbate the problem, the circuits are often densely mounted on printed circuit boards.
This increase in the amount of heat generated in a given unit area has led to a demand to increase the rate at which heat is transferred away from the circuits in order to prevent the circuits from becoming damaged or destroyed due to exposure to excessive heat. To increase the amount of heat that such circuits can withstand, the circuits can include internal heat pathways which channel or otherwise direct heat away from the most heat-sensitive regions of the circuits.
Although this internal heat pathway technique increases the amount of heat which the circuits can withstand while still operating, one problem with this internal heat pathway technique is that the amount of heat generated by the circuits themselves often can exceed the amount of self-generated heat which the circuits can successfully expel as they are caused to operate at higher powers. Furthermore, other heat generating circuit components mounted on printed circuit boards proximate the circuits of interest further increase the difficulty with which heat can be removed from heat sensitive circuits. Thus, to increase the rate at which heat is transferred away from the circuits, a heatsink is typically attached to the circuits.
Such heatsinks typically include a base from which project fins or pins. The fins or pins are typically provided by metal extrusion, stamping or other mechanical manufacturing techniques. The heatsinks conduct and radiate heat away from the heat generating and thermally vulnerable regions of circuits. To further promote the heat removal process, fans are typically disposed adjacent the heatsink to blow or otherwise force air or gas through the sides of the fins or pins of the heatsink.
One problem with this approach, however, is that the amount of air or other gas which a fan or blower can force through the heatsink fins/pins is limited due to the significant blockage of gas flow pathways due to the fins/pins themselves. Furthermore, in a densely populated printed circuit board (PCB) or multi-circuit module (MCM), other circuit components and mechanical structures required to provide or mount the PCB or module present additional blockage to gas pathways and also limits the amount of gas flow through the heatsink thus limiting the effectiveness of the heatsink. Thus, the ability of such conventional heatsinks and heatsink fan assemblies is limited and is not sufficient to remove heat as rapidly as necessary to ensure reliable operation of state of the art devices, circuits and modules having increased thermal cooling requirements.
It would, therefore, be desirable to provide a heat removal system which requires a relatively small surface area for mounting and which is capable of removing an amount of heat which is greater than the amount of heat removed by conventional heatsinks requiring a like amount of surface area. It would be further desirable to provide a method and apparatus for producing a heatsink member as part of the heat removal system, and to provide such a member in a cost-effective and repeatable manner.
In accordance with the present invention, a heat removal system includes a heatsink having a base and a plurality of heat conducting folded fin members projecting from a first surface of the base and arranged to leave an open space on the first surface of the base. At least one thermally conductive slug projects from the center of the fin members. A gas circulating system (e.g. a fan) is disposed over the slug and fin members. With his particular arrangement, a heat removal system (a fan-heat sink assembly) which rapidly removes heat from devices, circuits and modules including high power CPU chips and custom ASICS is provided. By disposing the gas circulating system above the base and the thermally conductive slug and fins, the gas circulating system increases the amount of gas flow through and around the heat conducting members and thermally conductive plate. In a preferred embodiment, the gas circulating system blows gas downward toward a PC board on which a heat generating device is disposed. The folded fin members and slug provide increased heat sinking capability. In one embodiment, the folded fin heat sink members are arranged in a circular shape and are attached to a surface of a central slug having a right circular cylinder shape and disposed in the center of the circle formed by the folded fin members. The gas circulating system may be provided as a fan or squirrel cage type blower. In some embodiments it may be preferable to position the gas circulating system below, rather than above the base plate. In such embodiments, the base plate should have one or more openings therein to allow the passage and flow of gas through and around the thermally conductive members and thermally conductive plate. The assembly will be self aligning and self jigging and the attachment means can be by soldering in a belt furnace.
The heatsink assembly folded fin member may be arranged to provide a plurality of fins and troughs. The sidewall of a fin is provided with at least one aperture. The top surface of the fin is closed, thereby permitting the fin to operate as a plenum of sorts. Different aperture patterns, shapes, and sizes are provided to produce the desired cooling for a particular application. The apertures may be provided on only a single sidewall of the fin, or may be provided on both sidewalls of the fin. The bottom of the troughs may also be closed.
A method of producing the folded fin heatsink member is also disclosed. A piece of material is provided having a plurality of holes disposed therein. The material is aligned between a stripper plate and an upper die. Next a fold is punched into the material with a die block and a fin forming punch. The folded piece is retracted from an upper die and the process repeated until the desired number of fins has been produced. Then the folded fins are separated from the unformed material, thereby providing the folded fin member. The apparatus for forming the folded fin member comprises an upper die having a recess formed therein, the upper die being movable between a first upper die position and a second upper die position. The apparatus further includes a pilot pin movably disposed within said upper die and a stripper plate disposed below said upper die and having an aperture disposed there through. The stripper plate is capable of supporting the piece of material being formed into the folded fin heatsink member. A die block is disposed beneath the stripper plate, with the die block movable between a first die block position and a second die block position. The apparatus further includes a forming punch extending from said die block and movable through the aperture in the stripper plate and into the recess of the upper die.